Re multiple birth facts (or multiple death facts). Slightly summing up, my supposition is that most people will only have one birth fact and accommodate any lack of clarity by using things like date ranges or higher levels of place (e.g. a country instead of a town), plus lots of notes against the fact or the citation.
There are those who will use multiple birth facts (or death facts, etc) - those people will, I guess, make extensive use of multiple birth etc.
I would suggest that the first group - whether they realise it or not - are using FH to record conclusions - albeit conclusions that can be modified by notes such as "Frankly, I don't believe a word of it...."
The second group are probably much more aware that they are using FH to record evidence, rather than conclusions.
Quite how good FH is at recording evidence, especially contradictory evidence, I'm not sure - slightly better now stuff can be flagged - but I'd want to see better treatment of alternative relationships.
I think I only have one multiple birth individual - the infamous Edith Roya whose names and birthplaces are legion, so it became simpler to record multiple births (as the encompassing birthplace would be "Planet Earth")
My tongue is in my cheek over this but it appears to me that the first group (those who have a single birth fact) are fact-lumpers, while those with multiple birth facts are fact-splitters... And it appears that I'm a source-splitter and a fact-lumper. Wonder what that means? :-)